In the latest twist in an increasingly complex case of the gruesome murder of three Salvadorean politicians, allegedly assassinated by corrupt Guatemalan police officers, the four main suspects have themselves been shot dead in jail.

What happened inside the jail is still unclear

A spokeswoman for the Guatemalan national police confirmed late on Sunday the deaths of the four men, identified as Luis Arturo Herrera, head of the police's organised crime unit, and three of his officers.

Maria Jose Fernandez said that she did not know who had killed the men, who were being held at the notoriously violent El Boqueron prison, 70km (43 miles) east of Guatemala City.

Initial reports from the scene, quoted in a Salvadorean newspaper on Monday, said that hired assassins had entered the jail during visiting time and had carried out the killings during a power cut later that same day.

However, police said that a riot had broken out in the prison on Sunday afternoon, initiated by members of the violent Mara Salvatrucha gang who dominate the jail, although they could not say whether the four victims were shot during or after the disturbances began.

One member of the Mara Salvatrucha told reporters by telephone from inside the prison that they had rioted out of fear of being blamed for the police officers' deaths.

By late Sunday the rioters were still holding a number of hostages inside the jail complex.

Theories

Luis Herrera and his fellow officers were arrested on 22 February for the abduction and murder of Salvadorean of the politicians William Pichinte, Eduardo D'Aubuisson and Jose Ramon Gonzalez - all members of El Salvador's ruling Arena party - and their driver.

Early reports said the killing of the Salvadoreans was political

Their charred bodies had been found three days earlier on the outskirts of Guatemala City, where they had been due to arrive on a visit from El Salvador.

As the days have gone by there have been a wide variety of versions circulating about why they were targeted.

Early reports suggested that it was a political killing, since Eduardo D'Aubuisson was the son of Roberto D'Aubuisson, the man widely believed to have run El Salvador's right-wing death squads in the 1980s.

Other sources quoted by the Guatemalan press said the victims had been carrying drug money in a hidden compartment in one of their vehicles and were killed as part of a vendetta between rival gangs.

The head of the presidential human rights office in Guatemala, Frank LaRue, told the BBC he could not confirm or deny that version, but said that he was convinced "organised crime" was behind the killings.

He also confirmed that his government had requested help in the investigations from the FBI.

'Weakness'

For his part, El Salvador's chief of police, Rodrigo Avila, has said he believes the three politicians and their driver were killed "by mistake", and that the assassins were "tricked" into believing they were targeting drug traffickers by those who had hired them.

Mr Avila also said that on their arrest, the four police officers had confessed to their interrogators, a version that was later denied by the Guatemalan authorities.

However, GPS tracking devices in the police officers' car appeared to link them directly to scene of the crime.

With the suspected gunmen now dead, investigations will now centre on the larger question of who was behind the killings.

The ability to assassinate high-profile politicians in broad daylight and then order the death in custody of the principal suspects, suggests a powerful and well-organised criminal syndicate is involved.

Mr LaRue said that infiltration of the Guatemalan police by organised crime was nothing new and reflected the continuing weakness of the security apparatus in the country.

Neither was it the first time, he said, that politicians from Central America had become caught up in criminal activities - if that were indeed the case.